modify the sudoers file under etc directory
command
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sudo visudo
add the following line at the end of the file like for user saiful
saiful ALL=NOPASSWD: /usr/sbin/mkdir,/usr/sbin/touch
Fatal error: Allowed memory size of 67108864 bytes exhausted (tried to allocate 20480 bytes) in /home/r8424051/public_html/nibatech.com/wiki/wp-includes/cache.php on line 652